The present invention relates to a data symbol reader for reading encoded information, such as a data symbol, and, in particular, to a non-contact type data symbol reader, that is, a data symbol reader that is not brought into contact with a plane of the data symbol in the reading process. The present invention is particularly applicable to a data symbol reader for reading a two-dimensional data symbol, such as a monochrome mosaic pattern.
In general, when a data symbol is to be read, the data symbol reader is brought into contact with a surface on which the two-dimensional data symbol is formed and is arranged such that, in this position, an image of the data symbol is formed on a CCD (Charge Coupled Device) by an imaging lens. This arrangement is referred to as a contact type data symbol reader.
However, in order to increase the range of use of a data symbol reader, recent designs have been directed to a non-contact type data symbol reader in which the data symbol reader does not have to be brought into contact with the surface on which the two-dimensional data symbol is formed.
However, with the non-contact type data symbol reader, because symbol reader is held at a distance from the plane of the data symbol, it is not easy for a user to ensure that a data symbol is in a symbol read area. That is, for a contact-type data symbol reader, a data symbol can be easily positioned in the symbol read area because the data symbol reader is close to or brought into contact with the plane of the data symbol, whereas for a non-contact type data symbol reader, the symbol read area is not defined in the plane of the data symbol.